javascript - Save CoffeeScript json object data inside a Rails variable -

i have js.coffee.erb file , in file there function gets 'equipment' json object (in javascript) , pastes of data html.
json object saved in variable called eqp.

each equipment has category (reference other table object).
in json object, there equipment.category_id, category name wrote statement:

$("#display_equipment_category_value").html <%= category.find(eqp.category_id).name %> 

the problem can't defined rails variable called eqp because it's not rails object.

how save js json eqp.category_id inside rails variable?

set_equipment = (eqp) ->      <% cat_id =  ?????  %>      -     # save eqp.category_id cat_id     $("#display_equipment_category_value").html <%= category.find(cat_id).name %> 

i'm not sure if it's correct answer because seems ineffective, works fine i'll use it:

set_equipment = (eqp) ->       // creating empty string variable result category name     cat = "";       // bringing categories db , save them json object      <% all_cat = category.all %>     categories = <%= all_cat.to_json %>       // comparing each category equipment category_id      $.each categories, (i, v) =>         cat = v.name if (v.id == eqp.category_id)        // display category name in html      $("#display_equipment_category_value").html cat